<select class="form-control">
    <optgroup label="A">
      <option>Alabama</option>
      <option>Alaska</option>
      <option>Arizona</option>
      <option>Arkansas</option>
    </optgroup>
    <optgroup label="C">
      <option>California</option>
      <option>Colorado</option>
      <option>Connecticut</option>
    </optgroup>
    <optgroup label="D" disabled="">
        <option>Delaware</option>
    </optgroup>
  <option>Florida</option>
  <option>Georgia</option>
  <option>Hawaii</option>
  <option>Idaho</option>
  <option>Illinois</option>
  <option>Indiana</option>
  <option>Iowa</option>
  <option>Kansas</option>
  <option>Kentucky</option>
  <option>Louisiana</option>
  <option>Maine</option>
  <option>Maryland</option>
  <option>Massachusetts</option>
  <option>Michigan</option>
  <option>Minnesota</option>
  <option>Mississippi</option>
  <option>Missouri</option>
  <option>Montana</option>
  <option>Nebraska</option>
  <option>Nevada</option>
  <option>New Hampshire</option>
  <option>New Jersey</option>
  <option>New Mexico</option>
  <option>New York</option>
  <option>North Carolina</option>
  <option>North Dakota</option>
  <option>Ohio</option>
  <option>Oklahoma</option>
  <option>Oregon</option>
  <option>Pennsylvania</option>
  <option>Rhode Island</option>
  <option>South Carolina</option>
  <option>South Dakota</option>
  <option>Tennessee</option>
  <option>Texas</option>
  <option>Utah</option>
  <option>Vermont</option>
  <option>Virginia</option>
  <option>Washington</option>
  <option>West Virginia</option>
  <option>Wisconsin</option>
  <option>Wyoming</option>
</select>